Seal assembly

ABSTRACT

A seal assembly, for setting at a predetermined depth in a conduit penetrating subterranean formations, having an elongate mandrel; an elongate tubular surface; an expansible tubular seal element; supporting and compression means for compressing the seal; slips; collet latch for releasably maintaining a set position; interconnection and release means for releasably connecting with a setting tool; connection means for connecting with a terminal device; and characterized by one or more of the desirable features as follows: (1) a bypass means for bypassing fluid when the seal element is not set and blocking flow of fluid once the seal element has been set; (2) a balancing chamber and piston for reducing the force the collet latch is required to sustain; and (3) a safety means for preventing unsetting of the retainer means as long as the differential pressure across the seal is too great. Specific and preferred structures are also disclosed.

United States Patent 1 Tamplen 51 Mar. 27, 1973 SEAL ASSEMBLY [76] Inventor: Jack W. Tamplen, RR. 2, Celina,

Tex. 75009 [22] Filed: Oct. 18, 1971 [21] Appl. No.: 190,085

Primary Examiner-James A. Leppink Attorney-William T. Wofford et al.

l3 El [57] ABSTRACT A seal assembly, for setting at a predetermined depth in a conduit penetrating subterranean formations, having an elongate mandrel; an elongate tubular surface; an expansible tubular seal element; supporting and compression means for compressing the seal; slips; collet latch for releasably maintaining a set position; interconnection and release means for releasably connecting with a setting tool; connection means for connecting with a terminal device; and characterized by one or more of the desirable features as follows: (1) a bypass means for bypassing fluid when the seal element is not set and blocking flow of fluid once the seal element has been set; (2) a balancing chamber and piston for reducing the force the collet latch is required to sustain; and (3) a safety means for preventing unsetting of the retainer means as long as the differential pressure across the seal is too great. Specific and preferred structures are also disclosed.

17 Claims, 7 Drawing Figures SEAL ASSEMBLY BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to subsurface well apparatus and, more particularly, to a seal assembly for setting at a predetermined depth in a conduit penetrating subterranean formations.

2. Description of the Prior Art In completing a well for producing fluids from subterranean formations, it has been frequent conventional practice to set a seal means to separate different zones, or depths, in the conduit. The separation may be for one of several reasons; for example, to separate productive formations. Myriad seals and assemblies for setting the seals have been developed in the prior art. The seals have served their purpose although they have been less than totally satisfactory. Insofar as I am aware, however, the seal assemblies of the prior art have not provided the following desirable features: (I) a seal assembly bypassing fluid before the seal element is set and blocking flow of the fluid once the seal element has been set; (2) a force reducer in the form of a balancing chamber and piston reducing the force that the latching means of the seal assembly is required to withstand because of the differential pressure across the seal; and (3) a safety feature which prevents the seal assembly from being blown longitudinally of the conduit by being released while the differential pressure thereacross is above a dangerous differential pressure that is great enough to cause damage as by blowing the seal assembly longitudinally of the conduit.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic elevational view of one embodiment of this invention suspended by way of a setting tool and a wireline in a cased wellbore.

FIGS. 2A and 2B are partial cross sectional views of, respectively, the upper and lower portions of a seal assembly of one embodiment of this invention with the seal assembly in the unset condition for being run into the well.

FIGS. 3A and 3B are partial cross sectional views of, respectively, the upper and lower portion of the embodiments of FIGS. 2A and 2B, showing the seal assembly in the set condition, or position.

FIG. 4 is a partial cross sectional view of the latching means of the embodiment of FIGS. 2A and 3A.

FIG. 5 is a cross sectional view of a releasing mandrel, or pulling nose.

DESCRIPTION OF THE PREFERRED EMBODIMENTS It is an object of this invention to provide a seal assembly that obviates the disadvantages of the prior art structures and provides one or more of the desirable features delineated hereinbefore.

This and other objects will become apparent from the following descriptive matter taken in conjunction with the drawings.

Referring to the drawings, FIG. 1 illustrates sea] assembly 1!; setting tool 13; collar locator and cable head assembly 15; all of which are suspended from a wireline 17 in a section of conduit 19 in a borehole 21 penetrating subterranean formations 23. The conduit 19 may be casing or tubing and the seal assembly 11 will be sized accordingly. A terminal device 25 is ordinarily connected onto the seal assembly 11. The terminal device 25 may comprise, for example, a tubing safety valve or plug and a pressure equalizer, such as described and claimed in my U.S. Pat. No. 3,581,891, entitled Pressure Equalizing Apparatus.

The collar locator and cable head assembly 15 and the setting tool 13 are conventional and well known and need not be described in detail herein. For example, a setting tool is described and claimed in U. S. Pat. No. 3,266,575, issued Aug. 16, 1966, to Harrold D. Owen. Any other apparatus may be employed as the setting tool to set the seal assembly 11 as long as it is capable of producing the requisite relative longitudinal movement of the subassemblies of the seal assembly 11.

The seal assembly 11 comprises the following elements or subassemblies, specific embodiments of which are illustrated in FIGS. 2A and 2B and delineated hereinafter: an elongate mandrel such as inner mandrel 27; an elongate tubular surface such as defined by the surface 29; an expansible tubular seal element 31; support means 33 for supporting the seal element 31 against longitudinal compression; compression means 35 for longitudinally compressing the seal element 31; retainer means 37 for retaining, or anchoring, the seal assembly 11 at a predetermined depth in conduit 19; latching means 39 for releasably latching the seal assembly in the set position; first and second interconnection and release means 41 and 43 for releasably connecting the seal assembly 11 with the setting tool 13; connection means 45 for connecting the terminal device 25 with the seal assembly 11; bypass means 47 for bypassing fluid when the seal assembly 11 is in the unset position; force reducer means 49 for reducing the force that the latching means is required to sustain when the seal assembly 11 is in the set position; and the across the seal assembly 11 is greater than the dangerous differential pressure described hereinbefore.

As illustrated, the inner mandrel 27 forms an inner tubular element which allows forming a cohesive entity of the seal assembly 11. The inner mandrel 27 traverses the length of the seal assembly, affording a good base that may be connected with the setting tool 13 at its upper end and connected with a terminal device 25 at its lower end.

The elongate tubular surface 29 is defined by an outer surface of a reduced portion 53 of an expander mandrel 55. The elongate tubular surface 29 affords a smooth sealing surface which the seal element 31 may sealingly engage.

The expansible tubular seal element 31 is carried by the elongate tubular surface 29 and is adapted to expand radially, or transversely, outwardly in response to longitudinal compression. The expansible tubular seal element 31 is referred to also hereinafter as simply the seal element 31. It has a resiliency and a return memory such that it will return to an elongate structure and reduce its expanded outside diameter sufficiently to clear the walls of the conduit 19 to facilitate removal even after prolonged emplacement in the conduit. The seal element 31 is disposed intermediate first and second annular shoulders 57 and 59 of, respectively, support means 33 and compression means 35 for effecting compression of the seal element 31. A specific and preferred embodiment of the seal element 31 is described and claimed in my co-pending application Ser. No. 190,086, entitled Seal that is Responsive to Either Mechanical or Pressure Force; filed even date 'herewith. That description is embodied herein by reference for additional details and the following description of the seal element 31 is less detailed, in the interest of brevity.

The seal element 31 comprises at least one annular ridge 61 and preferably comprises a plurality of annular ridges for reasons which will become apparent from the description hereinafter. Each annular ridge has an outer diameter portion 63 connected with two inner diameter portions 65 and 67 via two respective side walls 69 and 71. The side walls 69 and 71 define in cross section an angle a therebetween that is greater than 90 in the unset condition such that relatively small movement of the inner diameter portions 65 and 67 toward each other initially effect relatively large expansion of the outer diameter portion 63 outwardly to engage the conduit 19. The angle a is less than 90 in the set position, FIG. 313, such that the compressive force able to be generated in effecting aseal by engagement of the outer diameter portion 63 with the conduit 19 is greater than the first compressive force exerted by the compression means 35 in compressing the seal element 31. The seal element 31 effects sealing engagement of the inner diameter portions 65 and 67 with the elongate tubular surface 29 and of the outer diameter portion 63 with the conduit 19. For example, assume the seal element 31 initially has sides that define in cross section an angle a of 120 therebetween and two equal angles of 30 with the elongate tubular surface 29. Under the force of 260 pounds compression by the compression means 35, the exemplified seal element 31 will generate a compressive force of about 970 pounds against the conduit 19 and against the elongate tubular surface 29 when the seal is expanded laterally, or set, with the angle a about 30, as illustrated in FIG. 3B. In the set position, the illustrated seal element 31 is responsive to both longitudinal compressive force and pressure force, either of which will maintain the sealing engagement of the seal element 31 with the respective tubular surface 29 and conduit 19. Expressed otherwise, even if the first compressive force generated by the compression means 35 is subsequently released, the seal element 31 will continue to hold a contained pressure greater than the dangerous differential pressure. The seal element 31 has sufficient resiliency and a return memory such that after the compressive force exerted by the annular shoulders is released, it will elongate and contract laterally against a low pressure differential that is below the dangerous differential pressure. The elongation and lateral contraction releases the seal element 31 from sealing engagement with the conduit 19.

Suitable back-ups 72 are provided at each end of the seal element 31 to prevent extrusion of the seal element 31 under high differential force imposed thereacross. Specifically, the seal back-ups 72 comprise coil springs 74 that are embedded in rubber 76 such that the force due to differential pressure will be shared by both the front and back portions of the coil springs 74; the rubber 76 also serving to prevent laying over of the coil springs 74 which deleteriously and adversely affects the life and performance of the back-ups 72.

The types of materials ordinarily employed in this art may be employed for making the seal element 31. The materials should be resistant to attack by the well fluids and have the desired resiliency and elasticity to fulfill the requisites delineated hereinbefore. Ordinarily, the elastomeric materials such as the synthetic rubbers or the natural rubbers that have been treated to be resistant to attack by hydrocarbonaceous fluids are employed. Typical of the synthetic rubbers are Neoprene and Buna-N. if desired, thermoplastic materials may be employed if they have the requisite physical properties. Even metals may be employed, particularly for seal installations subjected to extreme temperatures.

The support means 33 comprises the expander mandrel 55 carrying the first annular shoulder 57 for supporting one end of the seal element 31. The support means 33 is, in turn, supported by the retainer means 37 as will become clear from the descriptive matter with respect to the latter and the safety means 51.

The compression means 35 comprise the seal backup housing 73 with its second annular shoulder 59 for compressing the seal element 31; and the fish neck housing 75. The seal back-up housing 73 is movable longitudinally with respect to the support means 33 for compressing the seal element 31 therebetween. As will become apparent from the operational description hereinafter, the first compressive force for compressing the seal element 31 is transmitted by way of the top 77, fish neck housing 75, and seal back-up housing 73.

The retainer means 37 is sometimes referred to as an anchor means and comprises at least one set of slips 79 conduit 19 as the setting inclines 81 and 83 are moved toward each other. To move the setting incline 81 with respect to the setting incline 83 on the inner mandrel 27, the expander mandrel 55 must be moved relative to the inner mandrel 27. Accordingly, the expander mandrel 55 has its reduced portion 53 defining a cylindrical body and upwardly extending collet fingers 147 having enlarged upper ends 148. The collet fingers 147 and enlarged upper ends 148 are disposed in chamber of seal back-up housing 73. The collet fingers traverse interiorly of an internally extending shoulder 146 of the seal back-up housing 73. As illustrated in FIG. 2B, the internally extending shoulder 146 traps the enlarged upper ends 148 against the inner mandrel 27 after assembly. Consequently, as the seal back-up housing 73 is moved upwardly relative to the inner mandrel 27 the enlarged upper ends 148 are pulled upwardly by the internally extending shoulder 146. The enlarged upper ends 148 thus pull the expander mandrel 148 and the setting incline 81 upwardly. The chamber 165 does, however, allow limited longitudinal movement of the enlarged upper ends 148 therewithin, as illustrated in FIG. 3B. Garter springs 91 are provided to retain the slips 79 in place and to cause them to move inwardly once the setting inclines 81 and 83 are moved apart. A plurality of garter springs 91 are preferably employed such that they fill the recess on the slips 79 and maintain alignment of the slip segments. The respective relative movements of the setting inclines 81 and 83 iongitudinally with respect to each other is effected by respective relative longitudinal movements of the inner mandrel 27 and its bottom sub 85 with respect to the seal back-up housing 73. When the movements effect relative downward movement of seal back-up housing 73, the compressive force is transmitted by way of seal element 31 and expander mandrel 55 to force the slips 79 outwardly to engage the conduit 19, and set the seal assembly 11. The compressed, or set, position is maintained by the latching means 39.

The latching means 39 comprise annular teeth 93 carried by the fish neck housing 75 and matching teeth 95 carried by collet fingers 97. As illustrated in FIG. 4, the teeth 93 and 95 comprise thread serrations having mating angles. The angles 99, 103 and 105 are chosen so as to be complementary and such that the teeth, or thread serrations, will engage each other in a conforming fit, or mate. The teeth 93 and 95 have respective mating surfaces inclined at an angle 99 such that when the teeth are engaged with a force across them, they will tend to remain engaged. Each collect finger 97 can be moved toward disengagement by way of an inward force of sufficient magnitude on its inclined surface 101. The magnitude of the force required may be large, however. A sleeve 107 is retained in place on the inner mandrel 27 by way of shear pins 109. As illustrated, the sleeve 107 has a mating inclined surface 111, FIG. 3A, that will engage the inclined surfaces 101 of the collet fingers 97 to disengage the teeth 93 and 95 by moving the collect fingers 97 inwardly. The unlatching of the latching means 39 is effected in response to relative downward movement of the sleeve 107 following shearing of the shear pin 109. The movement of sleeve 107 downwardly may be stopped, however, without disengaging the teeth 93 and 95 if the differential pressure is greater than the dangerous differential pressure, as will become clear from the operational description later hereinafter.

The first and second interconnection and release means 41 and 43 are provided for connecting the inner mandrel 27 and the compression means 35 of the seal assembly 1 1 with, and releasing them from, appropriate relatively longitudinally movable subassemblies of a setting apparatus, or setting tool. As illustrated, the first and second interconnection and release means 41 and 43 are provided for connecting the inner mandrel 27 and the compression means 35 with individual piston and cylinder assembly portions of the setting tool 13 and for releasing the inner mandrel 27 and comprcssion means 35 from the setting tool 13.

Specifically, the first interconnection and release means 41 comprises shear sleeve 113. The shear sleeve 113 has two threads. The bottom thread 115 engages the thread 1 17 of the inner mandrel 27. The-top thread 119 engages the thread 121 of an adapter rod 123 that is employed for connecting with the bottom piston of the setting tool 13. As illustrated, the adapter rod 123 has an upper thread 125 for screwing into the lower piston of the setting tool 13. The shear sleeve 113 has shear recess 139, or ring of reduced wall thickness, for shearing at a predetermined level of stress to release the adapter rod 123 for freeing the setting tool 13 from the seal assembly 11, as shown in FIG. 3A.

The second interconnection and release means 43 comprises collet fingers 127 of the collet sleeve 129 screwed within setting sleeve 130 engaging internal fish neck 131. The collet fingers 127 are maintained in engagement with the internal fish neck 131 by way of annular shoulder 133 of adapter rod 123. By the interrelationship of the adapter rod 123 in engagement with the inner mandrel 27, and the collet fingers 127 retained in engagement with the internal fish neck 131, with the top 77 of the fish neck housing 75 engaging the setting sleeve 130, the seal assembly 11 is retained in its most elongate position, as illustrated in FIGS. 2A and 2B. Collet fingers 127 are flexible, however, and when the annular shoulder 133 is moved upwardly from beneath the ends 141 of the collet fingers 127, they may flex inwardly, or laterally, to be pulled from engagement with the internal fish neck 131 to release the setting sleeve 130 and the collet sleeve 129 from the fish neck housing 75. i

The setting tool; with the adapter rod 123, the setting sleeve 130, and the collet sleeve 129 attached; is then withdrawn from the set seal assembly 11.

The connection means 45 are illustrated as comprising a bottom thread that is carried by the inner mandrel 27. The bottom thread may be directly on the inner mandrel 27, or it may include, as illustrated, bottom sub 85 with the desired thread 143 thereon. As illustrated, the connection means comprises the thread 143 on bottom sub 85 which is in turn threadedly connected with the inner mandrel 27, as illustrated in FIGS. 2B and 3B. Any other connection means may be employed as long as it is appropriate for effecting the desired interconnection with the terminal device 25,

FIG. 1.

The bypass means 47 comprises any suitable mean that will bypass fluid when the seal assembly 11 is not set and block flow of fluid when the seal assembly 11 is set. The bypass means 47 is structured such that closure of the bypass means 47 is effected by the relative longitudinal movement between the support, means 33 and the compression means 35 when they are operated into the set position. As illustrated in FIG. 2B, the bypass means 47 comprises the slots 145 intermediate collet fingers 147 that are connected with an annular cylindrical body 149; and a seal means, such as O-ring 151, positioned with respect thereto such 'that fluid may bypass through the slots 145 in the unset position but may not bypass when the'seal means engages the continuous outer surface of the cylinder 149, as illustrated in FIG. 3B. Expressed otherwise, the slot 145 is disposed adjacent the O-ring 151 in the unset position such that fluid can pass therethrough; whereas, the solid cylinder 149 is disposed adjacent the O-ring 151 in the set position, blocking passage of fluid. The fluid bypasses along the slots 145 intermediate the collet fingers 147, thence outwardly through aperture 150, in communication with the-pressure above the seal element 31. The cylinder 149may comprise, as illustrated, the same cylinder as the reduced portion 53 of the expander mandrel 55 to simplify construction of the telescoping elements.

The force reducer means 49 comprises means for reducing the total force required to be sustained by the latching means 39 in order to hold against the differential pressure across the seal element 31; and has a first portion that is connected with the inner mandrel 27 and a second portion that is connected with the compression means 35 As illustrated in FIGS. 2A and 3A, the force reducer means 49 comprises a balance chamber means 153, reduced to substantially zero in FIG. 2A, and piston means 155 that are vented to pressure on a predetermined side of the seal element 31. As illustrated, they are vented to the pressure below the seal element 31, by way of passage of the fluid along the interface between the inner mandrel 27 and the expander mandrel 55. Specifically, the walls 157 and 159 of the chamber means 153 are connected with the fish neck housing 75, which is a part of the compression means 35. On the other hand, the piston means 155 is integrally connected with the inner mandrel 27. The area of the surface 161 of the piston means 155 is such that it presents an effective area on which the pressure acts that is a predetermined proportion of the total area exposed to the differential pressure across the seal element 31. Consequently, the total force required to be sustained by the latching means 39 is reduced by the predetermined proportion. For example, it has been found advantageous to employ a piston surface 161 that affords an effective area equal to one-half of the total area over which the differential pressure would otherwise be acting; thereby reducing the force required to be sustained by the latching means 39 to one-half that which it would otherwise have to sustain.

The safety means 51 comprises the pressure-responsive aspect of the seal element 31 and double slip means having a second set of slips 163 in addition to the slips 79; the double slip means having the first and second opposed inclines 87 and 89 disposed contiguous first and second setting inclines 81 and 83 that match therewith for expanding the double slip means outwardly to set against the conduit. The respective inclines 81, 83, 87 and 89 have been described hereinbefore with respect to the retainer means 37. Their coaction in operation of the safety means 51 will be apparent from the descriptive matter in the operational section hereinafter. It is sufficient to note at this point that, as long as the seal element 31 maintains the dif-' ferential pressure, the first setting incline 81 maintains the first slips 79 engaging the conduit 19 responsive to a differential pressure greater than the dangerous dif ferential pressure in one direction; as with the greater pressure above the seal element 31; and the second setting incline 83 maintains the second slips 163 engaging the conduit 19 responsive to a differential pressure greater than the dangerous differential pressure in the other direction. It will be recalled that the seal element 31 is capable of maintaining its seal against a differential pressure greater than the dangerous differential pressure whether or not the latching means 39 have been unlatched to release the mechanical longitudinal compressive force that is normally maintained on the seal element 31 by the support means 33 and the compression means 35. Thus, it can be seen that the seal element 31, being pressure responsive, co-acts with the double acting slips 163 and 79 and inclines 81, 83, 87 and 89, to serve as the safety means 51 to prevent the inadvertent release, or unanchoring, of the seal assembly 11 at a differential pressure sufficient to blow it longitudinally of the conduit 19.

In operation of the illustrated embodiment, the seal assembly 11 is attached to the bottom of setting tool 13. The connection may be made directly as described hereinbefore. For review, that description delineated the connection as follows: (I) the adapter rod 123 is screwed into the bottom piston of the piston assembly portion of the setting tool 13 and into the shear sleeve 113 of the inner mandrel 27; and (2) the fish neck housing is connected with the cylinder assembly portion of the setting tool 13 by way of collet sleeve 129 and setting sleeve 130. The respective relatively longitudinally movable components are adjusted such that the annular shoulder 133 of the adapter rod 123 supports the ends 141 of the collet fingers 127 engaging the internal fish neck 131. Thus, the pressure setting tool, and the setting adapters hold the seal assembly 11 extended to its longest position, as illustrated in FIGS. 2A and 28. If desired, the inner mandrel 27 may be connected to the cylinder assembly portion of the setting tool 13 and the fish neck housing 75 connected with the piston assembly portion of the setting tool 13 by way of a suitable crossover adapter, or cross connector, that is conventional in this art.

The sealassembly l1 and the setting tool 13, with any other desired elements; such as, the collar locator and cable head assembly 15 and the terminal device25 described hereinbefore with respect to FIG. 1; are run on the wireline 17 into the conduit 19 in the wellbore. As indicated, the wireline 17 may be either electric line if electric firing is used, or a slick line if a percussion firing head is employed. When positioned at the desired depth, seal assembly 11 may be emplaced by firing the setting tool 13, by whichever of the indicated conventional systems is being employed. As is well understood, when the setting tool 13 has its charge fired, the inner piston assembly portion and the outer cylinder assembly portion move longitudinally with respect to each other; the piston assembly portion moving relatively upwardly while the cylinder assembly portion moves relatively downwardly. Consequently, the respectively connected elements and sub-assemblies of the seal assembly 11 move relatively upwardly and downwardly. Specifically, the inner mandrel 27 and the bottom sub move upwardly relative to the initially downwardly moving compression means 35. The relatively downwardly moving seal back-up housing 73 of the compression means 35 tends to compress the seal element 31 against the support means 33, consequently moving the expander mandrel 55 downwardly.

As the expander mandrel 55 is forced relatively downward toward the bottom sub 85, the slips 79 and 163 are forced outwardly by the coned surfaces, or inclines, 81 and 83 on the expander mandrel 55 and the bottom sub 85. The garter springs 91 whichhave been holding the slip segments 79 and 163 retracted and in alignment will be overcome, moving the slip segments 79 and 163 outwardly into contact with the conduit 19. As the slips 79 and 163 engage the wall of the conduit, the expander mandrel 55 will be stopped in its downward movement; forcing the seal back-up housing 73 to telescope downwardly over the reduced portion 53. This telescoping, or relative longitudinal movement, compresses the seal element 31 longitudinally, expanding it diametrally outwardly into contact with the wall of the conduit 19. The longitudinal compression of the seal element 31 also effects an expansion outwardly of the seal back-ups 72 into contact with the wall of the conduit 19. Specifically, the seal element 31 and the back-ups 72 are moved into the position shown in FIG. 3B with the results described hereinbefore with respect to the set position of the seal element 31.

Also, O-ring 151 which was disposed adjacent slots 145 of the bypass means 47, will be moved adjacent the non-colleted cylinder 149, or the reduced portion 53 of the expander mandrel 55; thereby preventing fluid from passing from the chamber 165 through the slots 145 and thence via the drilled holes, forming apertures 150, exteriorly of the fish neck housing 75 above the seal element 31. Expressed otherwise, the bypass means 47 is moved by the relative longitudinal movement of the support means 33 and the compression means 35 to stop the flow of fluid through the bypass apertures 150.

Simultaneously with the relative longitudinal movement between the inner mandrel 27 and the compression means 35, the internal thread serrations forming annular teeth 93 are moved downwardly over the matching teeth 95 of the collet fingers 97, thereby latching the latching means 39. Since the respective thread serrations are formed as described hereinbefore, the collet fingers 97 will flex inwardly and ratchet into the annular teeth 93 but will expand outwardly to latch the latching means 39 when attempts are made to reverse the relative longitudinal movement. As illustrated, the collet fingers 97 have sufficient end clearance that the upper colleted end 167 may flex inwardly sufficiently to clear the annular teeth 93. As the slips 79 and 163 and the seal element 31 are set more tightly, the shear load of the shear sleeve 1 13 will be exceeded and the sleeve will shear at the recess 139. As the shear sleeve 113 shears, there is a reaction force that causes the incline shoulder 169 of the inner mandrel 27 to forcefully engage the incline 171 of the collet fingers 97, more firmly latching the latching means 39.

The upward movement of the adapter rod 123 will move the annular shoulder 133 from beneath the ends 141 of the collet fingers 127 and allow the collet fingers 127 to flex inwardly when the setting tool 13 is pulled from the seal assembly 11. Thus, the seal assembly 11 will be left emplaced at the desired depth in the conduit 19, with the slips 79 and 163 and the seal element 31 set in engagement with the walls of the conduit 19, the bypass means 47 closed, the latching means 39 latched, and the setting tool sheared off, all as illustrated in FIGS. 3A and 3B.

With the seal assembly 11 latched in the set position, pressure is distributed; by suitable fluid flow from below the seal element 31, passing between the internal surface of the expander mandrel 55 and the external surface of the inner mandrel 27; into the chamber 165. Fluid may also pass between the internal surface of the seal back-up housing 73 and the inner mandrel 27 into the chamber means 153 of the balancing chamber, or force reducer means 49. As described hereinbefore,

the pressure in the balancing chamber means 153 serves to offset the force required to be sustained by the latch means 39 in maintaining the seal assembly 11 in the set position with the differential pressure across the seal element 31. Specifically, the force of the pressure below the seal element 31 exerts an upwardly acting component on the surface 161 of the piston means to partially counter the force of the pressure above the seal element 31 downwardly acting on the inner mandrel 27. The force may act on the inner mandrel 27 by way of the terminal device 25 connected with the connection means 45; it being recalled that the terminal element 25 ordinarily has a portion for controlling or blocking the flow of fluids therethrough.

Structurally, the piston means 155; with its seal, 0- ring forms a piston that is directly anchored by way of the inner mandrel 27 to the set slips 79 and 163. This direct anchoring of the piston means 155 removes this force from the latching means 39. Consequently, the only force acting on the latching means 39 is the area of the conduit 19 at the seal element 31 less the area of the piston means 155 times the pressure differential across seal element 31. With the specific embodiment delineated hereinbefore, the latching means 39 is required to support only approximately one-half as much as it would otherwise be required to support without the force reducer means 49. Similarly, when the greater pressure is applied from the top of the inner mandrel 27, the force due to its acting on the area from the outside of the piston means 155 to the internal area of the conduit 19 is transmitted directly through the fish neck housing 75, the seal back-up housing 73, the seal element 31, the expander mandrel 55 and onto the slips 79 and 163. Thus, with the higher pressure being applied from above, the force required to be sustained by the latching means 39 is only the area of the piston means 155 times the pressure differential across the seal element 31. Again, it can be seen that, when the exemplified force reducer means 49 is employed, the latching means is required to support only about onehalf as much force as it would otherwise be required to support.

From the foregoing description and figures, it can be seen that the lower slips 163 support, by way of inner mandrel 27 and latching means 39, the load across the seal assembly 11 when the pressure differential is from below. Likewise, the upper slips 79 support the load when the pressure differential is from above the seal element 31.

If it is desired to pull the seal assembly 11, it is pulled with a conventional shear-up, inside fishing neck type pulling tool with the pulling nose 179 illustrated in FIG. 5 attached to the end thereof.

The pulling nose 179 has an internal thread 181 at its lower end for attaching an equalizing prong, such as described in my above-referenced US. Pat. No. 3,581,819. The counter bore 183 and apertures 185 provide a passageway for fluid bypass through the pulling nose 179 during the pressure equalization.

A pulling tool, the pulling nose 179 and the equalizing prong (not shown) are assembled and connected to a conventional string of wireline tools and lowered into the tubing, using the appropriate lubricator at the well head on the surface. This procedure is conventional, is not being claimed per se, and need not be described in detail herein.

Upon reaching the seal assembly 11, the equalizing prong passes downwardly through the bore 187, FIG. 3A, of the inner mandrel 27, thereby engaging the equalizing subs opening sleeve (not shown). Downward jarring opens the equalizing sub and permits the shoulder 189 on the pulling nose 179 to engage the top end 191 of the sleeve 107, FIG. 3A, serving as the relief sleeve. Further downward jarring will shear the shear pins 109, permitting the matching inclined surface 111 at the lower end of sleeve 107 to engage the inclined surface 101 of the collet fingers 97. The force due to any pressure differential existing across the seal element 31 is transmitted into the latching means 39; and, specifically, into the surfaces of the teeth 93 and 95 inclined at the angle 99, FIG. 4, through the force applied by way of the inclined shoulders 169 and 171 of, respectively, the inner mandrel 27 and the upper end 167 of the collet fingers 97. This load is then transferred onto the latching means 39, and specifically tends to hold the teeth 93 and 95 engaged. Expressed otherwise, the fish neck housing 75 must be moved downwardly relative to the inner mandrel 27, overcoming the force due to differential pressure across the seal element 31 before the latching means 39 can be unlatched, as by movement of the upper end 167 of the collet fingers 97 inwardly to free the respective teeth 93 and 95. The force that can be generated by a string of wireline tools is generally not great enough to unlatch the latching means 39 until the pressure across the seal element 31 is below the dangerous differential pressure. Since the pressure differential across the seal element 31must be low before the force that can be generated by the string of wireline tools is adequate to unlatch the latching means 39, the seal assembly is safe even without the safety means 51.

In the event, however, that premature unlatching should occur, the safety means 51 prevents unanchoring at differential pressures greater than the dangerous differential pressure. To illustrate specifically, the inner mandrel 27 and the bottom sub 85 are held from moving by the lower slips 163 remaining engaged with, or anchored to, the conduit while the seal element 31, the seal back-up housing 73 and the fish neck housing 75 move upwardly to firmly engage the internal fishing neck 131 onto the pulling tool. The seal element 31, being a pressure energized seal, will remain sealed even though longitudinal compression no longer exists. Similarly, if premature unlatching occurs when the pressure differential exists from above the seal as sembly 11, the same conditions exist except that the inner mandrel 27 and the bottom sub 85 move downwardly while the seal element 31, the expander mandrel 55, the seal back-up housing 73 and the fish neck housing 75 remain stationery with the upper slips 79 anchored against the conduit 19.

As indicated hereinbefore, this ability for the slip means to remain engaged under the differential pressure, even though thelongitudinal compressive force has been released, is a safety'feature which reduces the possibility of the seal assembly 11 being blown up or down the hole when the pressure differential exists across the seal element 31 in either direction. Moreover, the safety condition is provided even though the pulling tool and the pulling nose 179 are completely engaged within the seal assembly 1 1. To release the slip means from their anchored position, it is necessary to move the inner mandrel 27 and bottom sub 85 a short distance downwardly if the higher pressure is below the seal element 31; or to move the expander mandrel 55 a short distance upwardly if the higher pressure is above the seal element 31. The slips will then retract back to their original position.

During the later stages of pulling the seal assembly 11 when the pressures are almost equalized, the latching means 39 may be unlatched, allowing the seal assembly 11 to elongate. This elongation opens the bypass means 47, allowing fluid to flow therethrough and allowing the pressure differential to approach zero more rapidly. The additional bypassing of fluid also speeds up reaching the respective low differential pressure at which the seal element 31 will unset, or release its sealing engagement with the conduit 19.

The seal element 31 will elongate and contract laterally to an unset, or non-sealing, position when the pressure differential drops below that producing a force that is equivalent to the internal stesss load, or return memory, of the seal element 31.

This invention provides a seal assembly 11 that may be easily set in a conduit for a wide variety of applications in addition to those implied hereinbefore. For example, the fish neck housing has a longitudinally extending section 199 defining a true bore 201 and a sealing interior surface for sealingly receiving a seal means of an additional element; such as, tubing, a pump, and the like. Specifically, the seal assembly 11 can be employed as a mandrel to support a regulator or the like; as a packer; as a pack-off anchor; as a pluggable packer; or as a pump seat.

From the foregoing descriptive matter, it can be seen that the invention provides the objects delineated hereinbefore. Specifically, the invention provides a seal assembly having the desirable features delineated hereinbefore.

Although the invention has been described with a certain degree of particularity, it is understood that the present disclosure has been made only by way of example and that numerous changes in the details of construction and the combination and arrangement of parts may be resorted to without departing from the spirit and the scope of the invention.

What is claimed is: I

1. A seal assembly for emplacement at a predetermined depth in a conduit penetrating subterranean formations comprising:

a. an elongate mandrel;

b. an elongate tubular surface;

c. an expansible tubular seal element carried by said elongate tubular surface, said seal element being adapted to expand transversely outwardly in response to longitudinal compression;

. support means having a first annular shoulder for supporting one end of said seal element;

e. compression means having a second annular shoulder for longitudinally compressing said seal element; said compression means being movable longitudinally with respect to said support means;

f. retainer means for anchoring said seal assembly at a predetermined depth in said conduit; said retainer means having at least one set of slips that are movable outwardly into engagement with said conduit responsive to relative longitudinal movement between said mandrel and said compression means;

g. latching means for latching said mandrel and said compression means in their set position compressing said seal element into sealing engagement with said conduit; said latching means being movable into a second position for unlatching said mandrel and said compression means;

h. first and second interconnection and release means for connecting said mandrel and said compression means of said seal assembly with individual relatively longitudinally movable portions of a setting tool and for releasing said mandrel and said compression means from said setting tool; and

i. bypass means for selectively bypassing fluid; said bypass means being structured such that closure thereof is effected by the relative longitudinal movement between said support means and said compression means when operated toward the .set position; and such that opening thereof is effected by the relative longitudinal movement between said support means and said compression means when operated away from said set position.

2. The seal assembly of claim 1 wherein said bypass means comprises collet fingers having slots therebetween and connected with an annular cylindrical body having a continuous sealing surface, and a seal means so positioned with respect thereto that fluid may bypass through said slots in the unset position but may not bypass when said seal means engages said continuous sealing surface responsive to said relative longitudinal movement of said support means and said compression means.

3. A seal assembly for emplacement at a predetermined depth in a conduit penetrating subterranean formations comprising:

a. an elongate mandrel;

b. an elongate tubular surface;

c. an expansible tubular seal element carried by said elongate tubular surface, said seal element being adapted to expand transversely outwardly in response to longitudinal compression;

d. support means having a first annular shoulder for supporting one end of said seal element;

e. compression means having a second annular shoulder for longitudinally compressing said seal element; said compression means being movable longitudinally with respect to said support means;

f. retainer means for anchoring said seal assembly at a predetermined depth in said conduit; said retainer means having at least one set of slips that are movable outwardly into engagement with said conduit responsive to relative longitudinal movement between said mandrel and said compression means;

g. latching means for latching said mandrel and said compression means in their set position compressing said seal element into sealing engagement with said conduit; said latching means being movable into a second position for unlatching said mandrel and said compression means;

h. first and second interconnection and release means for connecting said mandrel and said compression means of said seal assembly with in- .dividual relatively longitudinal movable portions of a setting tool and for releasing said mandrel and said compression means from said setting tool; and

i. force reducer means for reducing the total force required to be sustained by said latching means in order to hold against the differential pressure across said seal element; said force reducer means having a first portion that is connected with said mandrel and a second portion that is connected with said compression means.

4. The seal assembly of claim 3 wherein said force reducer means comprises a balancing chamber means and piston means that are vented to pressure on a predetermined side of said seal element; the walls of said chamber means being connected with one of said mandrel and said compression means and the piston means being connected with the other of said mandrel and said compression means; the area of said piston means exposed to the pressure within said chamber means being a predetermined proportion of the total area exposed to the differential pressure across the seal elements such that said total force required to be sustained by the latching means is reduced by said predetermined proportion.

S. The seal assembly of claim 4 wherein the piston means comprises the first portion of the force reducer means and the walls of the chamber means comprise the second portion thereof.

6. The seal assembly of claim 5 wherein the balancing chamber means and piston means are vented to pressure below said seal element.

7. A seal assembly for emplacement at a predetermined depth in a conduit penetrating subterranean formations comprising:

a. an elongate mandrel;

b. an elongate tubular surface;

c. an expansible tubular seal element carried by said elongate tubular surface, said seal element being adapted to expand transversely outwardly in response to longitudinal compression;

. support means having a first annular shoulder for supporting one end of said seal element;

e. compression means having a second annular shoulder for longitudinally compressing said seal element; said compression means being movable longitudinally with respect to said support means;

f. retainer means for anchoring said seal assembly at a predetermined depth in said conduit; said retainer means having at least one set of slips that are movable outwardly into engagement with said conduit responsive to relative longitudinal movement between said mandrel and said compression means;

g. latching means for latching said mandrel and said compression means in their set position compressing said seal element into sealing engagement with said conduit; said latching means being movable into a second position for unlatching said mandrel and said compression means;

h. first and second interconnection and release means for connecting said mandrel and said compression means of said seal assembly with individual relatively longitudinally movable portions of a setting tool and for releasing said mandrel and said compression means from said setting tool; and

i. safety means for preventing unanchoring of said retainer means as long as the differential pressure across said seal element is greater than a dangerous differential pressure that is sufficiently high to effect damage as by blowing the seal assembly longitudinally of the conduit.

8. The seal assembly of claim 7 wherein said safety means comprises double slip means having first and second slips, respective first and second opposed inclines, and first and second setting inclines that match respectively with said first and second opposed inclines for expanding said double slip means outwardly to anchor against said conduit responsive to relative longitudinal movement of said support means and said mandrel and the longitudinal compression of and setting of said seal element; said first setting incline maintaining said first slips engaging said conduit responsive to said dangerous differential pressure in one direction, and said second setting incline maintaining said second slips engaging said conduit responsive to said dangerous differential pressure in the other direction; and comprises the pressure energization capability of said seal element such that it retains its sealing engagement with the elongate sealing surface and the conduit whether or not said latching means is unlatched to release the mechanical longitudinal compressive force that has been maintained on said seal element by said support means and said compression means.

9. The seal assembly of claim 8 wherein said first and second setting inclines are disposed respectively above and below said first and second slips; wherein said first setting incline must be moved upwardly toward any higher pressure to unanchor said first slips after they have been anchored with a differential pressure from above said seal element; and wherein said second setting incline must be moved downwardly toward any higher pressure to unanchor said second slips after they have been anchored with a differential pressure from below said seal element.

10. The seal assembly of claim 9 wherein said first setting incline must be moved upwardly to unanchor said first slips and said second setting incline must be moved downwardly to unanchor said second slips.

11. The seal assembly of claim 9 wherein said elongate mandrel comprises an inner mandrel; wherein said first setting incline is connected with an expander mandrel of said support means; said expander mandrel has upwardly extending collet fingers having enlarged upper ends; wherein said compression means comprises a seal back-up housing that has a chamber receiving said collet fingers and said enlarged upper ends and allowing limited reciprocal longitudinal movement thereof; said seal back-up housing having an internally extending shoulder trapping said enlarged ends against said inner mandrel such that movement of said seal back-up housing longitudinally of said inner mandrel will move said expander mandrel and said first setting incline upwardly for unanchoring said first slips.

12. The seal assembly of claim 11 wherein said expander mandrel has an upper reduced portion defining a cylindrical body with a continuous sealing surface below said collet fingers; wherein a bypass aperture is provided through said internally extending shoulder and in fluid communication with slots intermediate said collet fingers when said seal assembly is in its unset position; and wherein a seal means is disposed in said internally extending shoulder above said bypass aperture such that said seal means engages said continuous sealing surface responsive to relative longitudinal movement of said seal back-up housing downwardly over the cylindrical body of said expanding mandrel.

13. The seal assembly of claim 8 wherein said double slip means comprise a plurality of discrete double slip segments having a recess between said first slips toward one end and said second slips toward the other end, and wherein a biasing and alignment means retains said double slip segments aligned and biased inwardly with their opposed inclines adjacent the respective setting inclines.

14. The seal assembly of claim 13 wherein said recess has a bottom external surface having a predetermined length and steeply inclined sides; and wherein said biasing and alignment means comprises a plurality of garter springs that are disposed in said recess, intermediate said sides thereof, and along substantially all said predetermined length of said bottom external surface.

15. The seal assembly of claim 7 wherein said elongate mandrel comprises an inner mandrel and said compression means comprises an outer housing; and wherein said latching means latches said inner mandrel to said outer housing in said set position such that said inner mandrel must be moved relative to said outer housing and against any pressure differential before said latching means can be unlatched.

16. The seal assembly of claim 15 wherein said latching means comprise annular teeth carried by said outer housing and matching teeth on collet fingers carried by said inner mandrel; said teeth comprising thread serrations having mating angles that are chosen so as to conformingly fit and having mating surfaces that are inclined at an angle such that when the teeth are engaged with a force across them, they remain engaged until there is movement of said inner mandrel relative to said outer housing; a space being provided about the free end of said collet fingers to allow inward flexure thereof; said collet fingers being adapted .to flex inwardly to effect ratchet engagement of said matching teeth with said teeth responsive to relative longitudinal movement between said inner mandrel and said outer housing; each said collet finger having an outwardly inclined surface adjacent its upper free end such that said collet fingers will flex inwardly sufficiently to unlatch said teeth responsive to a sufficient force on said inclined surface; each said collet finger also having a second and opposed incline adjacent its upper end, said second incline being disposed adjacent a shoulder on said inner mandrel for maintaining said matching teeth on said collet fingers latched responsive to a force by said shoulder on said inner mandrel; and wherein said inner mandrel has a sleeve shearably retained-in place; said sleeve having adjacent its lower end a third and mating inclined surface for engaging said outwardly inclined surface and forcing said collet fingers to flex inwardly and unlatch said teeth when a force of sufficient magnitude is imposed on said sleeve. v

17. The seal assembly of claim 7 wherein said compression means includes an outer housing and said outer housing has a longitudinally extending section defining a true bore and a sealing interior surface for sealingiy receiving a seal means of an additional element; such as, tubing, pump, and the like. 

1. A seal assembly for emplacement at a predetermined depth in a conduit penetrating subterranean formations comprising: a. an elongate mandrel; b. an elongate tubular surface; c. an expansible tubular seal element carried by said elongate tubular surface, said seal element being adapted to expand transversely outwardly in response to longitudinal compression; d. support means having a first annular shoulder for supporting one end of said seal element; e. compression means having a second annular shoulder for longitudinally compressing said seal element; said compression means being movable longitudinally with respect to said support means; f. retainer means for anchoring said seal assembly at a predetermined depth in said conduit; said retainer means having at least one set of slips that are movable outwardly into engagement with said conduit responsive to relative longitudinal movement between said mandrel and said compression means; g. latching means for latching said mandrel and said compression means in their set position compressing said seal element into sealing engagement with said conduit; said latching means being movable into a second position for unlatching said mandrel and said compression means; h. first and second interconnection and release means for connecting said mandrel and said compression means of said seal assembly with individual relatively longitudinally movable portions of a setting tool and for releasing said mandrel and said compression means from said setting tool; and i. bypass means for selectively bypassing fluid; said bypass means being structured such that closure thereof is effected by the relative longitudinal movement between said support means and said compression means when operated toward the set position; and such that opening thereof is effected by the relative longitudinal movement between said support means and said compression means when operated away from said set position.
 2. The seal assembly of claim 1 wherein said bypass means comprises collet fingers having slots therebetween and connected with an annular cylindrical body having a continuous sealing surface, and a seal means so positioned with respect thereto that fluid may bypass through said slots in the unset position but may not bypass when said seal means engages said continuous sealing surface responsive to said relative longitudinal movement of said support means and said compression means.
 3. A seal assembly for emplacement at a predetermined depth in a conduit penetrating subterranean formations comprising: a. an elongate mandrel; b. an elongate tubular surface; c. an expansible tubular seal element carried by said elongatE tubular surface, said seal element being adapted to expand transversely outwardly in response to longitudinal compression; d. support means having a first annular shoulder for supporting one end of said seal element; e. compression means having a second annular shoulder for longitudinally compressing said seal element; said compression means being movable longitudinally with respect to said support means; f. retainer means for anchoring said seal assembly at a predetermined depth in said conduit; said retainer means having at least one set of slips that are movable outwardly into engagement with said conduit responsive to relative longitudinal movement between said mandrel and said compression means; g. latching means for latching said mandrel and said compression means in their set position compressing said seal element into sealing engagement with said conduit; said latching means being movable into a second position for unlatching said mandrel and said compression means; h. first and second interconnection and release means for connecting said mandrel and said compression means of said seal assembly with individual relatively longitudinal movable portions of a setting tool and for releasing said mandrel and said compression means from said setting tool; and i. force reducer means for reducing the total force required to be sustained by said latching means in order to hold against the differential pressure across said seal element; said force reducer means having a first portion that is connected with said mandrel and a second portion that is connected with said compression means.
 4. The seal assembly of claim 3 wherein said force reducer means comprises a balancing chamber means and piston means that are vented to pressure on a predetermined side of said seal element; the walls of said chamber means being connected with one of said mandrel and said compression means and the piston means being connected with the other of said mandrel and said compression means; the area of said piston means exposed to the pressure within said chamber means being a predetermined proportion of the total area exposed to the differential pressure across the seal elements such that said total force required to be sustained by the latching means is reduced by said predetermined proportion.
 5. The seal assembly of claim 4 wherein the piston means comprises the first portion of the force reducer means and the walls of the chamber means comprise the second portion thereof.
 6. The seal assembly of claim 5 wherein the balancing chamber means and piston means are vented to pressure below said seal element.
 7. A seal assembly for emplacement at a predetermined depth in a conduit penetrating subterranean formations comprising: a. an elongate mandrel; b. an elongate tubular surface; c. an expansible tubular seal element carried by said elongate tubular surface, said seal element being adapted to expand transversely outwardly in response to longitudinal compression; d. support means having a first annular shoulder for supporting one end of said seal element; e. compression means having a second annular shoulder for longitudinally compressing said seal element; said compression means being movable longitudinally with respect to said support means; f. retainer means for anchoring said seal assembly at a predetermined depth in said conduit; said retainer means having at least one set of slips that are movable outwardly into engagement with said conduit responsive to relative longitudinal movement between said mandrel and said compression means; g. latching means for latching said mandrel and said compression means in their set position compressing said seal element into sealing engagement with said conduit; said latching means being movable into a second position for unlatching said mandrel and said compression means; h. first and second interconnection and release means for connecting said mandrel and said compression means Of said seal assembly with individual relatively longitudinally movable portions of a setting tool and for releasing said mandrel and said compression means from said setting tool; and i. safety means for preventing unanchoring of said retainer means as long as the differential pressure across said seal element is greater than a dangerous differential pressure that is sufficiently high to effect damage as by blowing the seal assembly longitudinally of the conduit.
 8. The seal assembly of claim 7 wherein said safety means comprises double slip means having first and second slips, respective first and second opposed inclines, and first and second setting inclines that match respectively with said first and second opposed inclines for expanding said double slip means outwardly to anchor against said conduit responsive to relative longitudinal movement of said support means and said mandrel and the longitudinal compression of and setting of said seal element; said first setting incline maintaining said first slips engaging said conduit responsive to said dangerous differential pressure in one direction, and said second setting incline maintaining said second slips engaging said conduit responsive to said dangerous differential pressure in the other direction; and comprises the pressure energization capability of said seal element such that it retains its sealing engagement with the elongate sealing surface and the conduit whether or not said latching means is unlatched to release the mechanical longitudinal compressive force that has been maintained on said seal element by said support means and said compression means.
 9. The seal assembly of claim 8 wherein said first and second setting inclines are disposed respectively above and below said first and second slips; wherein said first setting incline must be moved upwardly toward any higher pressure to unanchor said first slips after they have been anchored with a differential pressure from above said seal element; and wherein said second setting incline must be moved downwardly toward any higher pressure to unanchor said second slips after they have been anchored with a differential pressure from below said seal element.
 10. The seal assembly of claim 9 wherein said first setting incline must be moved upwardly to unanchor said first slips and said second setting incline must be moved downwardly to unanchor said second slips.
 11. The seal assembly of claim 9 wherein said elongate mandrel comprises an inner mandrel; wherein said first setting incline is connected with an expander mandrel of said support means; said expander mandrel has upwardly extending collet fingers having enlarged upper ends; wherein said compression means comprises a seal back-up housing that has a chamber receiving said collet fingers and said enlarged upper ends and allowing limited reciprocal longitudinal movement thereof; said seal back-up housing having an internally extending shoulder trapping said enlarged ends against said inner mandrel such that movement of said seal back-up housing longitudinally of said inner mandrel will move said expander mandrel and said first setting incline upwardly for unanchoring said first slips.
 12. The seal assembly of claim 11 wherein said expander mandrel has an upper reduced portion defining a cylindrical body with a continuous sealing surface below said collet fingers; wherein a bypass aperture is provided through said internally extending shoulder and in fluid communication with slots intermediate said collet fingers when said seal assembly is in its unset position; and wherein a seal means is disposed in said internally extending shoulder above said bypass aperture such that said seal means engages said continuous sealing surface responsive to relative longitudinal movement of said seal back-up housing downwardly over the cylindrical body of said expanding mandrel.
 13. The seal assembly of claim 8 wherein said double slip means comprise a plurality of discrete double slip segmenTs having a recess between said first slips toward one end and said second slips toward the other end, and wherein a biasing and alignment means retains said double slip segments aligned and biased inwardly with their opposed inclines adjacent the respective setting inclines.
 14. The seal assembly of claim 13 wherein said recess has a bottom external surface having a predetermined length and steeply inclined sides; and wherein said biasing and alignment means comprises a plurality of garter springs that are disposed in said recess, intermediate said sides thereof, and along substantially all said predetermined length of said bottom external surface.
 15. The seal assembly of claim 7 wherein said elongate mandrel comprises an inner mandrel and said compression means comprises an outer housing; and wherein said latching means latches said inner mandrel to said outer housing in said set position such that said inner mandrel must be moved relative to said outer housing and against any pressure differential before said latching means can be unlatched.
 16. The seal assembly of claim 15 wherein said latching means comprise annular teeth carried by said outer housing and matching teeth on collet fingers carried by said inner mandrel; said teeth comprising thread serrations having mating angles that are chosen so as to conformingly fit and having mating surfaces that are inclined at an angle such that when the teeth are engaged with a force across them, they remain engaged until there is movement of said inner mandrel relative to said outer housing; a space being provided about the free end of said collet fingers to allow inward flexure thereof; said collet fingers being adapted to flex inwardly to effect ratchet engagement of said matching teeth with said teeth responsive to relative longitudinal movement between said inner mandrel and said outer housing; each said collet finger having an outwardly inclined surface adjacent its upper free end such that said collet fingers will flex inwardly sufficiently to unlatch said teeth responsive to a sufficient force on said inclined surface; each said collet finger also having a second and opposed incline adjacent its upper end, said second incline being disposed adjacent a shoulder on said inner mandrel for maintaining said matching teeth on said collet fingers latched responsive to a force by said shoulder on said inner mandrel; and wherein said inner mandrel has a sleeve shearably retained in place; said sleeve having adjacent its lower end a third and mating inclined surface for engaging said outwardly inclined surface and forcing said collet fingers to flex inwardly and unlatch said teeth when a force of sufficient magnitude is imposed on said sleeve.
 17. The seal assembly of claim 7 wherein said compression means includes an outer housing and said outer housing has a longitudinally extending section defining a true bore and a sealing interior surface for sealingly receiving a seal means of an additional element; such as, tubing, pump, and the like. 